Processes and apparatus for reacting gaseous reactants containing solid particles

ABSTRACT

The present invention provides improved processes and apparatus for reacting high flow rates of one or more gaseous reactants in tubular reactors. The improved processes and apparatus allow such reactions to be carried out with a low pressure drop across the reactor and without excessive erosion due to solid particles carried with or picked up by the gaseous reactants. A process of this invention is basically comprised of the steps of swirling a gaseous reactant which may contain or pick up solid particles in a first annular plenum chamber followed by a second larger diameter annular plenum chamber and then introducing the gaseous reactant and solid particles into a reactor by way of two or more radial slots whereby said gaseous reactant and solid particles are caused to flow into said reactor and are uniformly distributed therein.

[0001] The present application is a continuation-in-part of U.S. patentapplication Ser. No. 09/361,003, filed Jul. 27, 1999.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to processes and apparatus forreacting high flow rates of gaseous reactants containing particulatesolids in tubular reactors, and more particularly, to reacting high flowrates of oxygen and titanium tetrachloride gas which can contain or pickup particulate solid contaminants in a tubular reactor at hightemperature to produce titanium dioxide.

[0004] 2. Description of the Prior Art

[0005] In reactions carried out in tubular reactors where high flowrates of gaseous reactants are injected into the reactors, problems withincomplete mixing and severe erosion of the side walls of the reactorsdue to the presence of particulate solid contaminants in the reactantscan occur. The incomplete mixing can cause less than desirable reactionresults and the erosion causes contamination of the products producedwith the materials forming the reactors as well as drasticallyshortening the lives of the reactor apparatus. For example, in theproduction of titanium dioxide, the gaseous reactants are heated oxygenand heated titanium tetrachloride gas which are combined in a tubularreactor at high flow rates. A high temperature oxidation reaction takesplace in the reactor whereby solid titanium dioxide particles areproduced. Occasionally, both the oxygen and the titanium tetrachloridegas streams utilized in the reaction contain or pick up particulatesolid contaminants which impinge on the surfaces of the reactorapparatus. Such particulate solid contaminants get into the gas streamsas a result of the passage of the gas streams through process equipmentand piping upstream of the reactor apparatus. The process equipment andpiping can contain particulate solid scale, solid particles fromfluidized beds, particulate welding slag and the like. Also, aparticulate solid scouring medium such as sand is often introduced intothe reactor apparatus to scour titanium dioxide deposited on the wallsof the reactor therefrom. The scouring medium occasionally finds its wayinto various upstream parts of the reactor apparatus and some of it ispicked up and carried by the gaseous reactant streams. For example, ifthe scouring medium is being introduced into the reactor apparatus whenthe flow of oxygen or titanium tetrachloride is shut down, the scouringmedium can flow out of the reactor into oxygen or titanium tetrachlorideintroduction apparatus, e.g., plenum chambers, connected to the reactor.

[0006] In attempts to solve the problems mentioned above, large plenumchambers have heretofore been utilized upstream of the reactor injectionpoints of gaseous reactants to trap contaminants therein, and thegaseous reactants have been injected through small gaps. The use ofsmall gaps results in high pressure drops which bring about good mixingof gases in the reactor, but the high pressure drops in the gaseousreactants require their pressurization which is very costly.

[0007] In order to operate with lower gaseous reactant pressure drops,the gaseous reactants have heretofore been tangentially injected intosmall annular plenum chambers which distribute them around two or moreslots through which the gaseous reactants flow radially into thereactor. The use of injection through the slots brings about lowpressure drops, but particulate solid contaminants carried or picked upby the gaseous reactants can be trapped in the annular plenum chamberswhich causes the plenum chambers to be rapidly eroded.

[0008] Thus, there are needs for improved processes and apparatus forreacting gaseous reactants in tubular reactors which bring about lowpressure drops across the reactor apparatus, more uniform distributionof the gaseous reactants and better mixing of the gaseous reactantswithout excessive erosion due to the presence of solid particles.

SUMMARY OF THE INVENTION

[0009] The present invention provides improved processes and apparatusfor reacting solid particle containing gaseous reactants in tubularreactors which meet the needs described above and overcome thedeficiencies of the prior art.

[0010] A process of the present invention for reacting a high flow rateof a gaseous reactant which can contain or pick up solid particles in atubular reactor is comprised of the following steps. The gaseousreactant to be injected is swirled in a first annular plenum chamberfollowed by a second larger diameter annular plenum chamber. Theswirling gaseous reactant is then introduced into the reactor by way oftwo or more radial slots communicating the reactor with the outlet ofthe second plenum chamber whereby solid particles carried with thegaseous reactant are caused to flow into the reactor with the gaseousreactant and are not trapped in the first or second plenum chambers. Theradial slots bring about the uniform distribution and alignment of theflow of the gaseous reactants and solid particles through the center ofthe reactor and thereby prevent incomplete mixing and erosion therein.In the production of titanium dioxide, the above described process ispreferably utilized for injecting high flow rates of heated oxygen intothe reactor.

[0011] Another process of this invention which can also be utilized forintroducing a high flow rate of a gaseous reactant into a tubularreactor which meets the above described needs is as follows. The highflow rate gaseous reactant which can contain solid particles is swirledin an annular plenum chamber which includes a boot formed therein forcatching the solid particles. The resulting substantially solid particlefree gaseous reactant is introduced into the reactor by way of two ormore radial slots communicating the reactor with the plenum chamber. Aconduit is optionally provided in the plenum chamber extending from theinterior of the boot to within one of the annular slots whereby the gaspressure differential between the boot and the slot causes the solidparticles caught in the boot to be swept through the conduit into thereactor. The radial slots are preferably slanted in the downstreamdirection to facilitate the uniform distribution and alignment of theflow of the gaseous reactant and solid particles (if any) through thecenter of the reactor and thereby prevent incomplete mixing and erosiontherein. In the production of titanium dioxide, this process ispreferably utilized for injecting high flow rates of heated titaniumtetrachloride into the reactor.

[0012] Apparatus for carrying out the above described processes are alsoprovided by the present invention.

[0013] It is, therefore, a general object of the present invention toprovide improved processes and apparatus for reacting solid particlecontaining gaseous reactants in tubular reactors.

[0014] A further object of the present invention is the provision ofimproved processes and apparatus for reacting high flow rates of oxygenand titanium tetrachloride gas which may contain or pick up particulatesolid contaminants in a reactor for producing titanium dioxide.

[0015] Other and further objects, features and advantages of the presentinvention will be readily apparent to those skilled in the art upon areading of the description of preferred embodiments which follows whentaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 is a top view of the solid particle containing gaseousreactant injection apparatus of this invention connected to a tubularreactor.

[0017]FIG. 2 is a side cross-sectional view taken along line 2-2 of FIG.1.

[0018]FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. 2.

[0019]FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 1.

[0020]FIG. 5 is a side cross-sectional view taken along line 5-5 of FIG.1.

[0021]FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. 5.

[0022]FIG. 7 is a cross-sectional view taken along line 7-7 of FIG. 5.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0023] Referring now to FIGS. 1 through 6 of the drawings, the apparatusof the present invention for injecting high flow rates of gaseousreactants containing solid particles into a tubular reactor isillustrated. The term “high flow rates” is used herein to mean flowrates in the range of from about 400 to about 3,000 or higher standardcubic feet per minute.

[0024] In FIG. 1, the apparatus of this invention is illustrated incombination with a tubular reactor for producing titanium dioxide fromheated oxygen and heated titanium tetrachloride gas streams which cancontain or pick up particulate solid contaminants and which are injectedat high flow rates into the tubular reactor. The tubular reactor can beof any known reactor design including those that are cooled with wateror other heat exchange medium, those which are not cooled, those thatare formed of a porous medium, etc.

[0025] The apparatus of FIG. 1, generally designated by the numeral 10,is comprised of a first form of gaseous reactant introduction apparatus12 and a second form of gaseous reactant introduction apparatus 14, bothfor introducing high flow rates of gaseous reactants which may containsolid particles into the tubular reactor 19. The apparatus 12 and 14 caneach be utilized for injecting any high flow rate gaseous reactant whichdoes or may contain solid particles into a tubular reactor. In apparatusfor producing titanium dioxide, the gaseous reactant introductionapparatus 12 and 14 can be utilized for introducing either the heatedoxygen or the heated titanium tetrachloride gas streams into thetitanium dioxide production reactor 19. However, the gaseous reactantintroduction apparatus 12 shown in FIGS. 1-4 is preferred forintroducing the heated oxygen stream into the reactor 19. The gaseousreactant introduction apparatus 14 shown in FIGS. 1 and 5-7 is preferredfor introducing the heated titanium tetrachloride gas stream which ishighly corrosive into the reactor 19.

[0026] In operation, both the apparatus 12 and the apparatus 14introduce high flow rates of gaseous reactants which may contain solidparticles into the tubular reactor 19 with low pressure drops, withuniform distribution and good mixing of the gaseous reactant streams inthe reactor and without excessive plenum chamber or reactor erosion dueto the presence of solid particles carried with the gaseous reactants.

[0027] As shown in FIGS. 1-4, the apparatus 12 is comprised of acylindrical gaseous reactant injection chamber 16 having an annularopening 17 around the periphery thereof and flange connections 18 and 20connected to the forward and rearward ends 19 and 21 thereof,respectively. A closing flange 22 is attached to the flange 18. Aconduit 24 is sealingly connected through the flange 22 and extends intothe cylindrical injection chamber 16. The conduit 24 is positionedcoaxially with the cylindrical injection chamber 16 and a second conduit26 which is also sealingly connected through the flange 22 is coaxiallydisposed around the conduit 24. An inlet flange 28 is connected to theconduit 24 and a flanged inlet connection 30 is connected to the conduit26. As indicated in FIG. 1, when the gaseous reactant introductionapparatus 12 is utilized with a water cooled titanium dioxide productionreactor, a source of auxiliary fuel, e.g., methane, propane or toluene,is connected to the inlet connection 30 of the conduit 26, and a sourceof reactor scouring medium is connected to the inlet connection 28 ofthe conduit 24. The auxiliary fuel is utilized to provide additionalheat and to stabilize the oxidization reaction in the reactor 19. Thefuel is oxidized to carbon dioxide and water and the water formedpromotes rutilization which improves the properties of the titaniumdioxide produced. The reactor scouring medium which can be sand, rocksalt, sintered titanium dioxide, compressed titanium dioxide or the likeis injected into the reactor apparatus to scour titanium dioxide fromthe cooled walls of the reactor. As the titanium dioxide is formed inthe reactor, some of it deposits on the walls of the cooled portions ofthe reactor, e.g., the part of the reactor cooled by water or othermeans. Unless removed, the titanium dioxide will continuously build upand substantially interfere with the cooling process. Thus, the scouringmedium must be continuously introduced into the reactor.

[0028] The injection chamber 16 also includes a pair of cooling waterjackets 32 and 34 for cooling the walls of the injection chamber. Inaddition, an annular heat shield 35 is disposed within the cylindricalgaseous reactant injection chamber 16 between the annular opening 17 inthe injection chamber and the forward end 19 thereof. The heat shield 35can be welded to the conduit 26 and it functions to shield the forwardend portion of the cylindrical gaseous reactant injection chamber 16from the heat produced by the heated gaseous reactant (heated oxygen)introduced through the annular opening 17 thereof. Also, as will bedescribed fuher hereinbelow, a deflector 37 for deflecting the flow ofthe heated oxygen introduced into the injection chamber 16 by way of theopening 17 and causing it to be uniformly distributed is attached to therearward end portion 39 of the conduit 26.

[0029] A first annular plenum chamber 36 is provided having an annularoutside wall 38, a side 40 sealingly attached to the exterior of thegaseous reactant injection chamber 16 and an annular side outlet 42. Asbest shown in FIG. 4, the first annular plenum chamber 36 also includesa tangential inlet 44 for receiving a high flow rate stream of heatedoxygen which may contain solid particles and causing the stream to swirlwithin the plenum chamber 36.

[0030] A second annular plenum chamber 46 having an annular outside wall47 and sides 48 and 50 is also sealingly attached to the exterior of theinjection chamber 16. The side 50 of the second plenum chamber 46 isattached to the outside wall 38 of the first plenum chamber 36 and thesecond plenum chamber 46 includes an annular side inlet 52 whichcoincides with the annular side outlet 42 of the first plenum chamber36. As shown in the drawings, the second plenum chamber 46 has a largerdiameter than the first plenum chamber 36 and the second plenum chamber46 covers the annular opening 17 around the periphery of the injectionchamber 16.

[0031] An annular slot 54 is formed within the second plenum chamber 46adjacent to the side 48 thereof by an annular plate 56 which issealingly attached to the exterior of the injection chamber 16 andextends to near the outside wall 47 of the second plenum chamber 46. Theannular slot 54 formed by the side 48 of the second plenum chamber 46and the annular plate 56 is sealingly attached over the annular opening17 in the injection chamber 16. Thus, as will be described in greaterdetail hereinbelow, the high flow rate of heated oxygen which maycontain solid particles conducted to the tangential inlet 44 of thefirst plenum chamber 36 is caused to swirl within the first plenumchamber 36 followed by swirling in the larger second plenum chamber 46and flowing out of the second plenum chamber 46 by way of the annularslot 54 into the interior of the injection chamber 16. Because theheated oxygen stream is first swirled within the smaller plenum chamber36 and then expanded and swirled in the plenum chamber 46, solidparticles contained in the stream are moved by centrifugal force to theoutside walls 38 and 47 of the plenum chambers 36 and 46 from where thesolid particles are caused to flow along with the heated oxygen throughthe slot 54 into the interior of the injection chamber 16 and the solidparticles are not trapped within the plenum chambers 36 and 46. As iswell understood by those skilled in the art, when solid particles aretrapped within a plenum chamber in which a high velocity gas stream isswirled, the solid particles erode and cut through the material formingthe plenum chamber in a very short period of time. As shown best in FIG.2, the outside wall 47 of the plenum chamber 46 is sloped outwardlytowards the side 48 thereof to facilitate the movement of the solidparticles into the slot 54.

[0032] As best shown in FIG. 3, the annular slot 54 includes a pluralityof spaced vanes 58 attached therein which form a plurality of radialslots 59 (FIG. 3) in the opening 54. The radial slots 59 function tostop the heated oxygen stream from swirling and uniformly distribute theflow of the heated oxygen stream and solid particles carried therewithinto and through the center of the injection chamber 16. The deflector37 attached to the interior end portion 39 of the conduit 26 functionsto cause the heated oxygen stream to be uniformly distributed and touniformly flow through the center of the injection chamber 16, thetitanium tetrachloride gas introduction apparatus 14 and the reactor 19thereby preventing incomplete mixing and erosion from taking place.

[0033] Thus, the process carried out in the apparatus 12 basicallycomprises the steps of swirling the gaseous reactant to be introducedinto the reactor 19 in the first annular plenum chamber 36 followed bythe second larger diameter annular plenum chamber 46. The swirlinggaseous reactant and solid particles carried therewith are introducedinto the reactor 19 by way of the radial slots 59 and the injectionchamber 16. That is, the gaseous reactant and solid particles flowthrough the radial slots 59 into the injection chamber 16 and then intothe reactor 19 and the solid particles are not trapped in the first orsecond plenum chambers. The radial slots 59 and the deflector 37disposed within the injection chamber 16 cause the gaseous reactant andsolid particles to flow into and through the injection chamber 16 in amanner whereby the gaseous reactant and solid particles uniformly flowthrough the centers of the injection chamber 16 and reactor 19 therebypreventing incomplete mixing and erosion therein. As mentioned, when theapparatus 12 is utilized in a process for producing titanium dioxide,the gaseous reactant introduced into the reactor 19 by way of theapparatus 12 is preheated oxygen, i.e., oxygen preheated to atemperature in the range of from about 1000° F. to about 1800° F.,preferably from about 1500° F. to about 1800° F. In addition, anauxiliary fuel is preferably introduced into the injection chamber 16and reactor 19 by way of the conduit 26, and a scouring medium forscouring the walls of the reactor are introduced into the injectionchamber 16 and reactor 19 by way of the conduit 24. Also, potassiumchloride, cesium chloride or the like can be added to the heated oxygenintroduced into the reactor 19 to control the particle size of thetitanium dioxide produced.

[0034] Referring now to FIGS. 1 and 5-7, the apparatus 14 forintroducing a high flow rate of a gaseous reactant (heated titaniumtetrachloride) which contains or may contain solid particles into thereactor 19 is illustrated. As best shown in FIG. 5, the apparatus 14includes a cylindrical gaseous reactant injection chamber 60 having aforward end 61 and a rearward end 65 adapted to be sealingly connectedto the upstream end of the tubular reactor 19 by way of a conicalconnecting pipe section 23 (FIG. 1) and having an annular opening 69formed therein around the periphery thereof. As will be understood bythose skilled in the art, the apparatus 14 can be formed of variousmaterials which have desired insulating, corrosion resistant and otherproperties. In the form illustrated in the drawings for use in apparatusfor producing titanium dioxide, the injection chamber 60 is comprised ofa cylindrical wall member 63 formed of a heat insulating refractorymaterial, a cylindrical member 64 formed of corrosion resistant metalmaterial and a cylindrical member 66 formed of a corrosion resistantsilicon carbide material. The annular opening 69 is preferably angledtowards the rearward end 65 of the injection chamber 60 as shown in FIG.5, and the annular opening 69 includes a plurality of spaced vanes 68(FIG. 6) disposed therein which form a plurality of radial slots 62therein. The radial slots 62 and annular opening 69 are angled in orderto prevent oxygen from entering them, the build up of oxides in theslots which can lead to plugging and to facilitate uniform distributionin the injection chamber 60. The vanes 68 can be integrally formed inthe cylindrical member 66 as shown in the drawings. Also, when auxiliaryfuel is utilized for providing additional heat as described above, thecylindrical wall member 63, the pipe section 67, the conical connectingpipe section 23 (FIG. 1) and the reactor 19 (FIG. 1) are all watercooled (not shown) to prevent damage thereto as a result of the hightemperatures involved.

[0035] An annular plenum chamber 70 having an outside wall 72 and sides74 and 76 formed of a metal such as steel is sealingly attached to theexterior of the cylindrical gaseous reactant injection chamber 60. Theinterior of the annular plenum chamber 70 is lined with a siliconcarbide corrosion resistant material 78 and a gasket material 80 isdisposed between the corrosion resistant material 78 and the outsidewall 72 and sides 74 and 76. As will be understood, insulating andcorrosion resistant materials or techniques other than those describedabove can be utilized in the apparatus 14.

[0036] For example, cylindrical member 64, which may be referred to as adistributor wear plate may be formed of a ceramic material as opposed tometal. As used herein and in the appended claims, a ceramic materialmeans a material manufactured by the action of heat on one or moreearthy raw materials. Examples of earthy raw materials useful in formingceramic materials are materials based on silicon or zirconium togetherwith aluminum and/or nitrogen, oxides of silicon, oxides of aluminum andsilicates.

[0037] Preferably, the ceramic material used in forming cylindricalmember 64 is selected from the group consisting of alumina, silica,alumina-silica, silicon carbides, silicon nitrides, and aluminumnitrides. More preferably, the ceramic material used in formingcylindrical member 64 is selected from the group consisting of siliconnitrides and aluminum nitrides. Ceramic materials formed ofsilicon-aluminum oxy nitride are most preferred. For example, theceramic material forming cylindrical member 64 can be formed of asilicon-aluminum oxy nitride comprising approximately 90% by weightsilicon nitride and approximately 10% by weight alumina, the weightpercents being based on the total weight of the ceramic material.

[0038] Silicon-aluminum oxy nitrides as a general class of ceramicmaterial consist of silicon nitride that is sintered with alumina(Al₂O₃), aluminum nitride (AlN), yttrium oxide (Y₂O₃) or some otherglass-forming oxide and fused at high temperature. The aluminastrengthens the ceramic and is itself very wear-resistant. An example ofa silicon-aluminum oxy nitride that is very suitable for use inconnection with the present invention is sold by International Syalonsin association with the trademark SYALON.

[0039] The use of a ceramic material in forming the cylindrical member64 greatly increases the service life of the member 64. Initially,corrosion-resistant metal material was used as the cylindrical member 64and was placed in service for approximately four (4) weeks. When themetal wear plate was removed, it exhibited signs of excessive abrasion.Other materials were utilized to test the ability to withstand theextreme conditions and the abrasive components passing therethrough.

[0040] It was discovered that greatly improved results were obtainedwhen the cylindrical member 64 was formed of a ceramic material,specifically SYALON. A cylindrical member 64 formed of SYALON was testedunder normal use conditions for a period of 14 weeks. The wear plate wassubsequently examined and showed abrasive-resistant abilities superiorto the corrosion-resistant metals that had been used previously.

[0041] As best shown in FIG. 7, a tangential inlet 82 for receiving ahigh flow rate stream of heated titanium tetrachloride gas whichcontains or may contain solid particles is attached to the plenumchamber 70. The tangential inlet 82 causes the titanium tetrachloridegas stream to swirl within the plenum chamber 70. A tangential boot 84is formed in the plenum chamber 70 downstream from the tangential inlet82 thereof for catching solid particles carried with the titaniumtetrachloride gas stream. The boot 84 includes a removable blind flange85 bolted thereto for periodically removing solid particles therefrom.Thus, as will be described further hereinbelow, the titaniumtetrachloride gas stream containing solid particles is swirled withinthe plenum chamber 70, the solid particles are caught in the boot 84 andthe resulting substantially solid particle free titanium tetrachloridestream flows into the injection chamber 60 by way of the radial slots 62and opening 69.

[0042] As best shown in FIG. 7, a conduit 86 can optionally be attachedwithin the plenum chamber 70 which has one end 88 extending into theboot 84 and the other end 90 extending into a radial slot 62. The gaspressure differential between the boot 84 and the radial slot 62 causessolid particles caught in the boot 84 to be swept along with a portionof the titanium tetrachloride gas stream through the conduit 86 into theinjection chamber 60 and the reactor 19.

[0043] The spaced vanes 68 disposed in the annular slot 69 which formthe radial slots 62 cause the titanium tetrachloride gas stream to slowor stop swirling and to be uniformly distributed in the injectionchamber 60 in a manner such that the gas stream and solid particles (ifany) flow through the center of the injection chamber 60 and reactor 19thereby preventing incomplete mixing and erosion therein. particles (ifany) flow through the center of the injection chamber 60 and reactor 19thereby preventing incomplete mixing and erosion therein.

[0044] Thus, the process carried out in the apparatus 14 basicallycomprises swirling the gaseous reactant that may contain or pick upsolid particles in the annular plenum chamber 70 which includes a boot84 formed therein for catching the solid particles. The resultingsubstantially solid particle free swirling gaseous reactant flows intothe injection chamber 60 by way of the radial slots 62 and annularopening 69. The solid particles caught in the boot 84 can be manuallywithdrawn therefrom periodically or they can be withdrawn continuouslyby the conduit 86 and caused to flow into a slot 62. As mentioned above,the plurality of radial slots 62 function to cause the gaseous reactantand solid particles (if any) to be uniformly distributed in theinjection chamber 60 and align the flow of the gaseous reactant andsolid particles through the center of the injection chamber 60.

[0045] As also mentioned, when the apparatus 14 is utilized in a processfor producing titanium dioxide, the gaseous reactant introduced into thereactor 19 by the apparatus 14 is titanium tetrachloride gas, i.e.,titanium tetrachloride gas preheated to a temperature in the range offrom about 350° F. to about 1800° F., preferably from about 750° F. toabout 1100° F. As will be understood, aluminum chloride can be added tothe heated titanium tetrachloride to enhance rutilization of theproduced titanium dioxide and make it more durable.

[0046] The process of the present invention carried out in the apparatus10 shown in FIG. 1 for producing titanium dioxide by reacting high flowrates of oxygen and titanium tetrachloride gases in the tubular reactor19 is generally carried out at a pressure of at least about 2 psig and atemperature of at least about 2200° F. Also, the temperatures of theoxygen and titanium tetrachloride streams are controlled so that thetemperature of the composite stream before reaction is in the range offrom about 900° F. to about 1800° F., preferably about 1450° F. Theprocess carried out in the apparatus 10 basically comprises the steps ofswirling heated oxygen which contains or may contain solid particles inthe first annular plenum chamber 36 followed by the second largerdiameter annular plenum chamber 46. The swirling oxygen is introducedinto the reactor 19 by way of the oxygen injection chamber 16 through afirst set of radial slots 59 communicating the injection chamber 16 withthe outlet of the second plenum chamber 46 whereby solid particlescontained therein are caused to flow into the injection chamber with theoxygen and are not trapped in the first or second plenum chambers. Theradial slots 59 are formed by a plurality of spaced vanes 58 disposed inthe annular opening 54. The radial slots 59 uniformly distribute andfacilitate the alignment of the flow of the oxygen and solid particlescarried therewith through the centers of the oxygen injection chamber16, the titanium tetrachloride injection chamber 60 and the reactor 19and thereby prevent incomplete mixing and erosion therein. The deflector21 also functions to align the flow of the heated oxygen and mix thecombustion products.

[0047] The titanium tetrachloride gas which contains or may containsolid particles is swirled in the third annular plenum chamber 70 whichincludes a boot 84 formed therein for catching the solid particles. Theresulting substantially solid particle free swirling titaniumtetrachloride gas is introduced into the injection chamber 60 and intothe reactor 19 by way of a second set of radial slots 62 communicatingthe injection chamber 60 with the plenum chamber 70. A conduit 86 isoptionally provided in the plenum chamber 70 extending from the interiorof the boot 84 to within a slot 62 whereby the gas pressure differentialbetween the boot 84 and the slot 62 causes the solid particles caught inthe boot to be swept through the conduit into the injection chamber 60and the reactor 19. The spaced vanes 68 disposed in the annular opening69 form the slots 62 which cause the titanium tetrachloride gas to beuniformly distributed in the injection chamber 60 and align the flow ofthe titanium tetrachloride gas and solid particles carried therewith (ifany) through the center of the injection chamber 60 and the reactor 19thereby preventing incomplete mixing and erosion therein.

[0048] As will now be understood by those skilled in the art, theimproved processes and apparatus of the present invention for reactinggaseous reactants containing solid particles at high flow rates intubular reactors make it possible to carry out the reactions at lowpressure drops with uniform distribution and better mixing of gases inthe reactors without excessive erosion. As will also be understood bythose skilled in the art, the improved processes and apparatus of thepresent invention can be utilized for reacting a variety of reactantscontaining solid particles at high flow rates and temperatures. Theprocesses and apparatus are particularly suitable for reacting preheatedoxygen and preheated titanium tetra- chloride containing solid particlesin tubular reactors for producing titanium dioxide. In addition, theyare suitable for reacting preheated oxygen with other preheated metalchlorides such as silicon tetrachloride, zirconium tetrachloride,aluminum tetrachloride and the like.

[0049] Thus, the present invention is well adapted to carry out theobjects and attain the ends and advantages mentioned as well as thosewhich are inherent therein. While numerous changes may be made by thoseskilled in the art, such changes are encompassed within the spirit ofthis invention as defined by the appended claims.

What is claimed is:
 1. An improved apparatus for introducing a high flowrate of a gaseous reactant which contains or picks up solid particlesinto a tubular reactor comprising: a cylindrical gaseous reactantinjection chamber having a closed forward end and a rearward end adaptedto be sealingly connected to the upstream end of said tubular reactorand having an annular opening around the periphery thereof; a firstannular plenum chamber having an outside wall and at least one sidesealingly attached to the exterior of said gaseous reactant injectionchamber, said first plenum chamber having an annular side outlet andhaving a tangential inlet for receiving a high flow rate stream of saidgaseous reactant containing solid particles and for causing said streamto swirl therein; a second annular plenum chamber having an outside walland sides and having a larger diameter than said first plenum chambersealingly attached to the exterior of said gaseous reactant injectionchamber, said second plenum chamber having an annular side inletsealingly attached to said annular side outlet of said first plenumchamber; an annular slot formed within said second plenum chamberadjacent to the side thereof opposite from said annular side inletthereof, said annular slot being sealingly attached over said annularopening in said gaseous reactant injection chamber and extending to nearthe outside wall of said second plenum chamber; and a plurality ofspaced vanes attached within said annular slot to thereby form two ormore radial slots therein.
 2. The apparatus of claim 1 which furthercomprises a gaseous reactant deflector disposed within said cylindricalgaseous reactant injection chamber for aligning and distributing saidgaseous reactant therein whereby it flows through the center of saidtubular reactor.
 3. The apparatus of claim 1 wherein said gaseousreactant is heated oxygen and the reaction carried out in said tubularreactor is the high temperature production of titanium dioxide.
 4. Theapparatus of claim 3 which further comprises a first conduit sealinglyextending into said cylindrical gaseous reactant injection chamber andpositioned coaxially therewith for discharging a reactor scouring mediumtherein.
 5. The apparatus of claim 4 which further comprises a secondconduit sealingly extending into said cylindrical gaseous reactantinjection chamber and positioned coaxially therewith and with said firstconduit for discharging auxiliary fuel therein.
 6. The apparatus ofclaim 5 which further comprises at least one cooling water jacketsealingly attached to the exterior of said cylindrical gaseous reactantinjection chamber.
 7. The apparatus of claim 6 which further comprises aheat shield disposed in said cylindrical gaseous reactant injectionchamber between said annular opening therein and said closed forward endthereof.
 8. The apparatus of claim 1 , the cylindrical gaseous reactantchamber comprising a cylindrical corrosion resistant member at the rearend thereof.
 9. The apparatus of claim 8 , said cylindrical corrosionresistant member being formed of a ceramic material.
 10. The apparatusof claim 9 , wherein said ceramic material is selected from the groupconsisting of alumina, silica, alumina-silica, silicon carbides, siliconnitride and aluminum nitrides.
 11. The apparatus of claim 10 , whereinsaid ceramic material is selected from the group consisting of siliconnitrides and aluminum nitrides.
 12. The apparatus of claim 11 , whereinsaid ceramic material is a silicon-aluminum oxy nitride.
 13. An improvedapparatus for introducing a high flow rate of a gaseous reactant whichcontains or picks up solid particles into a tubular reactor comprising:a cylindrical gaseous reactant injection chamber having a forward endand a rearward end adapted to be sealingly connected to the upstream endof said tubular reactor and having an annular opening formed thereinaround the periphery thereof, said annular opening having a plurality ofspaced vanes disposed therein to thereby form two or more radial slotstherein; and an annular plenum chamber having an outside wall and sidessealingly attached to the exterior of said cylindrical gaseous reactantinjection chamber over said annular opening, having a tangential inletfor receiving a high flow rate stream of said gaseous reactantcontaining solid particles and for causing said gaseous reactant toswirl in said plenum chamber, said annular plenum chamber also includinga tangential boot formed therein downstream from said tangential inletfor catching said solid particles contained in said gaseous reactant.14. The apparatus of claim 13 which further comprises a conduit attachedwithin said plenum chamber having one end extending into said boot andthe other end extending into one of said radial slots in saidcylindrical gaseous reactant injection chamber.
 15. The apparatus ofclaim 13 wherein said gaseous reactant is heated titanium tetrachloridegas and the reaction carried out in said tubular reactor is the hightemperature production of titanium dioxide.
 16. The apparatus of claim15 which further comprises an internal liner formed of corrosionresistant material disposed in said annular plenum chamber.
 17. Theapparatus of claim 15 wherein said annular opening in said cylindricalgaseous reactant injection chamber and said radial slots formed thereinare angled towards said rearward end thereof.
 18. The apparatus of claim13 , wherein said cylindrical gaseous reactant chamber has a wear platecomprised of a corrosion resistant material at the rear end thereof. 19.The apparatus of claim 18 , wherein said corrosion resistant material isformed of a ceramic material.
 20. The apparatus of claim 19 , whereinsaid ceramic material is selected from the group consisting of alumina,silica, alumina-silica, silicon carbides, silicon nitrides and aluminumnitrides.
 21. The apparatus of claim 20 wherein said ceramic material isselected from the group consisting of silicon nitrides and aluminumnitrides.
 22. The apparatus of claim 21 wherein said ceramic material isa silicon-aluminum oxy nitride.
 23. An improved apparatus forintroducing high flow rates of oxygen and titanium tetrachloride gaswhich contain or pick up solid particles into a tubular reactorcomprising: a cylindrical oxygen injection chamber having a closedforward end and a rearward end and having an annular opening around theperiphery thereof, a first annular plenum chamber having an outside walland at least one side sealingly attached to the exterior of saidcylindrical oxygen injection chamber, said first plenum chamber havingan annular side outlet and having a tangential inlet for receiving ahigh flow rate stream of heated oxygen containing solid particles andfor causing said stream to swirl therein, a second annular plenumchamber having an outside wall and sides and having a larger diameterthan said first plenum chamber sealingly attached to the exterior ofsaid oxygen injection chamber, said second plenum chamber having anannular side inlet sealingly attached to said annular side outlet ofsaid first plenum chamber; an annular slot formed within said secondplenum chamber adjacent to the side thereof opposite from said annularside inlet thereof, said annular slot being sealingly attached over saidannular opening in said cylindrical oxygen injection chamber andextending to near the outside wall of said second plenum chamber; aplurality of spaced vanes attached within said annular slot to therebyform two or more radial slots therein; a cylindrical titaniumtetrachloride gas injection chamber having a forward end sealinglyconnected to said rearward end of said cylindrical oxygen injectionchamber and a rearward end connected to the upstream end of said tubularreactor and having an annular slot formed therein around the peripherythereof, said annular slot having a plurality of spaced vanes disposedtherein to thereby form two or more radial slots therein; and a thirdannular plenum chamber having an outside wall and sides sealinglyattached to the exterior of said cylindrical titanium tetrachloride gasinjection chamber, having a tangential inlet for receiving a high flowrate stream of heated titanium tetrachloride gas containing solidparticles and for causing said titanium tetrachloride gas to swirl insaid plenum chamber, said third annular plenum chamber also including atangential boot formed therein downstream from said tangential inlet forcatching said solid particles contained in said titanium tetrachloridegas.
 24. The apparatus of claim 23 which further comprises a conduitattached within said third plenum chamber having one end extending intosaid boot and the other end extending into one of said radial slots insaid cylindrical titanium tetrachloride gas injection chamber.
 25. Theapparatus of claim 23 which further comprises an oxygen deflectordisposed within said cylindrical oxygen injection chamber fordistributing and aligning said oxygen therein whereby it flows throughthe center of said tubular reactor.
 26. The apparatus of claim 23 whichfurther comprises a first conduit sealingly extending into saidcylindrical oxygen injection chamber and positioned coaxially therewithfor discharging a reactor scouring medium therein.
 27. The apparatus ofclaim 26 which further comprises a second conduit sealingly extendinginto said cylindrical oxygen injection chamber and positioned coaxiallytherewith and with said first conduit for discharging auxiliary fueltherein.
 28. The apparatus of claim 27 which further comprises a heatshield disposed within said cylindrical oxygen injection chamber betweensaid annular opening therein and said closed forward end thereof. 29.The apparatus of claim 23 which further comprises an internal linerformed of corrosion resistant material disposed in said third annularplenum chamber.
 30. The apparatus of claim 29 wherein said annular slotand said radial slots in said cylindrical titanium tetrachloride gasinjection chamber are angled towards said rearward end of said injectionchamber.